Wash your Hands with Water and Soap. The Science Behind It.

wash your hand the science behind it

By: Eileen Ruiz, PhD


During this coronavirus outbreak, experts are telling us to wash our hands with water and soap.

The World Health Organization (WHO) state that people should “wash their hands frequently with soap and water” to prevent infection with the novel coronavirus.
Soap is the best defense against diseases. It prevents and stop the virus spreading, therefore, helps control the infection rates.

Then, why water and soap are so effective?

Soap dissolves the lipid membrane and the virus becomes inactive…, it falls apart.


Let’s start by understanding what a virus is and how is the coronavirus structure.

What is a virus?

Viruses are particles composed mainly of genetic material known as nucleic acids (either RNA or DNA) and proteins.  The proteins are like a protective coat, called capsid.  The capsid may be surrounded by an additional coat called the envelope.

Viruses are not living organisms as for example, bacteria.  A virus is a particle. It requires a living organism to replicate.  They invade cells of other living things (host cells) and use those cells to multiply. The virus particle attached to the host cell, penetrate it, and then uses the host cell’s machinery to replicate its own genetic material.

Coronavirus Structure

Coronaviruses (CoVs) are enveloped RNA viruses.  It is composed of ribonucleic acid (RNA), proteins and lipids.

The virus is characterized by protein spikes that project from their surface.

cdc coronavirus
Illustration Source: CDC

The coronavirus is named after the crownlike spikes that protrude from its surface. The spikes are proteins that project from their surface.

Coronavirus particles are surrounded by an envelope of lipid molecules. This “oily” envelop can break apart on contact with soap.

coronavirus structure
Illustration Source: New York Times


Soap has a hybrid structure. It is like a pin-shaped molecule.  Soap is an “amphiphile molecule:  it has a hydrophilic head that bonds with water and a hydrophobic tail that repels water and link with the lipids.


Illustration Source:
 Brookhaven National Lab   
Soap are molecules that have a dual nature. One end of the molecule is attracted to water and repelled by lipids (fats) and proteins. The other side of the molecule is attracted to lipids (fats) and is repelled by water.

How it works on the virus? One side of the soap molecule (the one that is attracted to lipid) buries its way into the virus’s lipid and protein shell. The chemical bonds holding the virus together are not strong, so it breaks the virus’s coat. The virus is pull apart, get soluble in water, and disintegrates.


Soap is a surfactant. One end of the soap molecule is hydrophilic (water-loving) and binds to water; the other end is hydrophobic (water-hating) and binds to oil molecules. In water, soap molecules form a ring around the drop of oil. This structure is called a micelle.


When you wash your hands with soap and water, microorganisms and viruses are surrounded with the soap molecules.  Hydrophobic tails attempt to evade water and try to “escape” from water.  It wedges into the lipid envelop of virus and bacteria, making them apart.  The structure rupture, proteins escape, and virus particle are inactive.

Hand Washing with Water and Soap

What happens when you wash your hands with water and soap?

Hand washing with soap uses mechanical action that loosens bacteria and viruses from the skin, rinsing them into the drain. Rubbing your hands together and rinsing provides a friction that destroys virus.

The Centers for Disease Control and Prevention (CDC) say that best practices for hand washing include rinsing the hands with water, applying soap and scrubbing the palms, the back of the hands, between the fingers, and under the fingernails.

Make sure to focus on places people tend to forget; the back of your hands, between your fingers, and under your nails, where microbes tend to build up.

Scrub for at least 20 seconds. A person should scrub for at least 20 seconds before rinsing the soap and drying the hands with a clean towel.  It is recommended at least 20 seconds to allow the soap to perform its chemical action and to interact with the virus particle.  It needs some time to work.

Even if it the soap does not destroy every virus particle, it helps to get rid from the hands with soap and water.

Drying is also important.  The friction with a clean hand towel removes bacteria and viruses that haven’t been removed with the soap and water.

The important is to remove the virus from your hands. This prevents the spreading to your body or other surfaces.  This is an important step to help protect yourself and protect others from this pandemic.



Anthony R. Fehr and Stanley Perlman. 2015. Coronaviruses: An Overview of Their Replication and Pathogenesis.  Methods Mol Biol.; 1282: 1–23. Retrieved from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4369385/

Corum, J. and Zimmer, C. (2020, March 13). The New York Times.  How Coronavirus Hijacks Your Cells. Retrieved from: https://www.nytimes.com/interactive/2020/03/11/science/how-coronavirus-hijacks-your-cells.html

Center for Diseases Control and Prevention. When and How to Wash Your Hands.  Retrieved from https://www.cdc.gov/handwashing/when-how-handwashing.html

Resnick, B. (2020, March 11). How soap absolutely annihilates the coronavirus. Retrieved from: https://www.vox.com/platform/amp/science-and-health/2020/3/11/21173187/coronavirus-covid-19-hand-washing-sanitizer-compared-soap-is-dope